Book excerpt: Terrorism: Commentary on Security Documents is a series that provides primary source documents and expert commentary on various topics relating to the worldwide effort to combat terrorism, as well as efforts by the United States and other nations to protect their national security interests. Volume 143, The Evolution of the Islamic State, focuses on the U.S. response to the Islamic State (IS) both in Syria and Iraq from a foreign policy standpoint and a military strategy perspective, as well as considering the impact of the rise of IS on the broader global jihadist movement. Consideration is also given to the importance of information warfare in countering IS's worldwide recruiting efforts via the Internet. This volume also includes documents examining related issues of great importance, including a report considering IS's financing, a report on the legal issues arising in connection with U.S. military action against IS, the role of Shia warlords and militias in Iraq in opposing IS, and the lessons that can be learned from the support provided to IS by European fighters.